CVE-2026-105659: high-severity vulnerability in mtrudel bandit
HTTP/2 blocked-send deadlines reset on every WINDOW_UPDATE, letting a trickle pin stream processes indefinitely in Bandit
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.7epss 0.6%
Uncontrolled Resource Consumption vulnerability in mtrudel bandit allows an unauthenticated remote attacker to pin HTTP/2 stream processes indefinitely via a trickle of small WINDOW_UPDATE frames. A stream whose response outruns the connection or stream send window blocks until the peer grants more window, and each block carries a 15 second deadline. Both deadlines restart whenever the peer makes partial progress. Bandit.HTTP2.Connection.finish_data/5 re-queues a partially advanced send in pending_sends with a fresh expires_at, so every WINDOW_UPDATE on stream 0, and every SETTINGS frame, resets the clock. Bandit.HTTP2.Stream.send_data/3 recurses on each stream WINDOW_UPDATE and re-arms a fresh after read_timeout. A peer that grants a few bytes every few seconds keeps the blocked stream process, its Plug state and any resource it holds mid-response alive for as long as it keeps dripping, and repeats this across streams and connections to exhaust server processes and memory.
The two paths are independent. The stream-level block is reached on its own by widening the connection window with a large WINDOW_UPDATE on stream 0 and shrinking the per-stream window with a small SETTINGS_INITIAL_WINDOW_SIZE, so closing only the connection-level path leaves it exploitable.
This issue affects bandit: from 1.4.0 before 1.13.0.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Affected products
mtrudel · banditRelated CVEs — mtrudel bandit
In the same product, most dangerous first.
CVE-2026-39804HIGHWebSocket permessage-deflate inflate has no output-size cap in banditEPSS 0.8%CVE-2026-75484MEDIUMHTTP/2 header field values containing CR, LF or NUL are passed to the application unvalidated in BanditEPSS 0.7%CVE-2026-42786HIGHWebSocket fragmented message reassembly unbounded in banditEPSS 0.6%CVE-2026-39803HIGHHTTP/1 chunked body reader ignores length cap in banditEPSS 0.6%CVE-2026-74836HIGHHTTP/2 connection-window starvation pins Plug processes indefinitely in BanditEPSS 0.6%CVE-2026-39806HIGHHTTP/1 chunked decoder infinite loop on requests with trailer fields in banditEPSS 0.6%
References
https://cna.erlef.org/cves/CVE-2026-105659.htmlhttps://github.com/mtrudel/bandit/commit/d88b21953c65061f21136ea76a89a4f95a2ac7a1https://github.com/mtrudel/bandit/commit/fff06efe3be962b484bd4d3eb339372fda5a231fhttps://github.com/mtrudel/bandit/security/advisories/GHSA-69m6-wcv4-rwcfhttps://osv.dev/vulnerability/EEF-CVE-2026-105659